Our work. 3D shadows in LiDAR point clouds, introduced in [1]}, are a physical phenomenon that is caused by occlusion of LiDAR laser pulses by objects in a scene. The authors leverage these shadow artifacts as a physical invariant to detect LiDAR spoofing attacks. We observed in Figure REF , that under object hiding attacks, the objects hidden by the adversary in the scene, are not detected by a DNN-based object detector, but still exist and occlude LiDAR pulses to leave behind shadow artifacts in the 3D point cloud. We leverage this observation and propose an obstacle detection methodology that searches a region of interest in a 3D point cloud for objects based on the shadow artifacts found in the 3D point cloud scene. Our proposed methodology of using shadows provides an alternate approach to detecting objects in a 3D scene and can be used as an orthogonal defense against object hiding attacks.
